a) field of the invention PA1 b) description of the prior art PA1 (a) pruning of tap roots emerging from the bottom of trees seedling boxes; and/or PA1 (b) uniform and complete root pruning of nursery trees grown in bags, thereby avoiding spiralling and perforation of the bags by rootlets; and/or PA1 (c) sclerosis of herbaceous plants and chemical pruning of roots from trees; and/or PA1 (d) pruning of roots penetrating into drainage pipes or disturbing ground-embedded structures such as basement or swimming pool walls; and/or PA1 (e) uniform pruning of rootlets of nursery stocks. PA1 (a) providing a root growth barrier consisting of a sheet of a non-woven fabric made of synthetic fibers coated with a water-insoluble polymeric binder in which is dispersed a water-insoluble inorganic copper compound in an amount effective to stop the growth of rootlets or radicles which come in contact with the fabric; PA1 (b) placing the tree-seedling boxes onto this barrier so that the bottoms of the boxes are in direct contact with the barrier; and PA1 (c) keeping the tree-seedling boxes on the barrier until the seedlings are ready to be removed from the boxes for transplantation; PA1 (a) providing bags of a water-permeable, non-woven fabric made of synthetic fibers coated with a water-insoluble polymeric binder in which is dispersed a water-insoluble inorganic copper compound in an amount effective to stop root growth; and PA1 (b) using the bags of step (a) as said bags to grow the nursery trees, PA1 (a) providing a weed growth and root emergence barrier consisting of a sheet of non-woven fabric made of synthetic fibers coated with a water-insoluble polymer binder in which is dispersed a water-insoluble inorganic copper compound in an amount effective to stop root growth; and PA1 (b) using the barrier of step (a) as said sheet of a landscape fabric;
The present invention relates to a method for controlling the growth of plant roots, which makes use of a durable root growth barrier consisting of a nonwoven, water-permeable fabric which has an adequate mechanical strength and is made of synthetic fibers coated with a polymeric binder in which is dispersed an inorganic copper compound in such an effective amount as to stop the growth of roots. The fabric may be used as a sheet, a sleeve or a bag, in order to chemically prune herbaceous or ligneous roots and prevent root spiralling.
Several methods have been developed over the past years in order to control the root growth of nursery stock, trees seedlings or mature trees.
Prior to commenting on these known methods, it is worth noting that nursery trees are usually grown in plastic containers provided with an aperture at their bottom. When the container is untreated, root spiralling may occur within the same while the plant is growing. Some roots may also emerge from the aperture at the bottom of the container. These emerging roots, called "tap roots", usually need to be cut to allow removal of the seedlings from the container. In practice, such a cutting is a great source of loss as a great number of seedlings are lost after transplantation due to the weakness of the damaged tap root.
To tentatively solve this problem, it has already been suggested to apply a coating consisting of a latex paint containing copper carbonate, onto the inner wall surfaces of the containers. By way of example, U.S. Pat. No. 4,916,856 to KINGHORN discloses a tree seedling box made of expanded polystyrene in which a plurality of castellated cavities are molded. Some portions of the surface of each cavity is coated with a copper paint or a latex paint containing copper carbonate, to prune the lateral roots of the tree seedling which come into contact therewith. In this patent, no means whatsoever are provided to prevent the tap roots from emerging from the opened bottom of each cavity. Accordingly, the tap roots must still be cut to allow removal of the seedlings, thereby causing damage to the trees during transplantation. The same occurs with all the types of coated or uncoated seedling boxer, presently known to the Applicant.
It has also been already suggested to replace plastic containers by burlap-type bags made of non-degradable non-woven fabrics. By way of example, U.S. Pat. Nos. 4,574,522 and 5,103,588 to REIGER disclose a method for controlling the root growth of nursery stock planted in the ground, wherein the roots are confined in the ground within a porous fabric container formed of needle punched continuous fibers, which acts as a mechanical barrier and promotes enlarged root nodule formation and root branching. With such a fabric container, part of the roots may spiralize within the container and rootlets may perforate the fabric and grow outside of the container. When transplanting the tree, the rootlets must be cut and transplantation shock is caused to the tree.
To tentatively avoid this problem, European laid-open patent application No. 307,720 to ZIMMERMAN discloses a geotextile membrane intended to be used as a mechanical barrier against plant root growth, in which are incorporated a plurality of slow release herbicide nodules. The herbicide which is released over the time, diffuses within the soil and acts as a root repellant agent. If this method is quite efficient, it does not prevent root spiralling and may generate pollution problems because of the herbicide released into the soil.
Last of all, it has also been suggested in the past to treat non-woven fabric or paper with chemical agents, especially fungicides, in order to prevent a decay of the same when used in a plant nursery. In this connection, reference can be made of U.S. Pat. No. 4,881,344 to FREY et al, which discloses a sleeve for use in plant germination, consisting of a non-woven cellulosic material treated with a polymer in which is dispersed a fungicide which may be an inorganic copper compound such as copper oxychloride, and whose purpose is exclusively to prevent the cellulose fibers from rooting. In this patent, it is disclosed that the sleeve must hold the roots together without, however, constituting an impermeable barrier for the roots. Accordingly, this patent does not call for, and actually teaches away from incorporating an inorganic copper compound into a fabric in such an effective amount as to stop root growth.